It's raining ideas on cloud seeding

November 1, 2003 — 11.00am

In August 1952, the RAF in Britain conducted Operation Cumulus, which involved gliders spraying clouds with dry ice, salt or silver iodide. Within days North Devon received 250 times its normal August rainfall. The town of Lynmouth was virtually washed away and 35 people were killed.

The link between the experiments and the flood has not been proved and cloud seeding over mainland Australia has also been inconclusive, according to the CSIRO.

But artificial rainmaking has its supporters, and a House of Representatives inquiry into water supplies has reignited their dispute with the CSIRO.

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Only Tasmania conducts cloud seeding, although in August, Snowy Hydro announced it would undertake a six-year $5 million trial in the Snowy Mountains, spraying clouds with silver iodide from generators on the ground.

Snowy Hydro predicts that snowfall could increase by 10 per cent and could deliver improved environmental flows to the Murray River.

The federal member for Mallee, the National Party's John Forrest, is Canberra's main advocate of cloud seeding.

A Melbourne weather research company, Australian Management Consolidated - which advocates the research of Israeli meteorologist Danny Rosenfeld - has also given evidence to the inquiry, which expects to finish its report early next year. AMC and Professor Rosenfeld say pollution from the Latrobe Valley and Melbourne has caused drought in Gippsland and the Alps by hindering the way clouds release rain. Cloud seeding would rectify the problem, they say.

The head of cloud seeding at Hydro Tasmania from 1990 to 2002, Ian Searle, said the process boosted rainfall in Tasmania's catchment areas by about 87 millimetres a year.

"In my view, the current CSIRO view is based on some rather unhappy experience they had and I think it's flawed," Mr Searle told The Age.

Monthly rainfall varies greatly from year to year. Trying to prove rain was caused by cloud seeding would require a long, expensive experiment. The CSIRO says the trials it conducted in Victoria in the 1970s and 1990s were unable to prove that cloud seeding worked.

Mr Searle disagrees. He said a trial in Tamworth in 1994 was inconclusive, but farmers found it useful. "In my view . . . it was an outstanding success," he said. "People would call up and say they got so much rain. They were very happy."

John Forrest - who says 40 countries, including South Africa, the United States and China practise weather modification - visited Texas last year, where cloud seeding is practised over a third of the state. Like AMC, he says pollution is hampering rainfall, but cloud seeding with salt will fix it.

"The (clouds) are full of aerosols and dust and industrial pollutants which impairs the rain-producing capabilities of the cloud . . . $5 million would give us a good (cloud seeding) program over six or seven years," he said.

The CSIRO says the money could be better spent elsewhere.

"Over Victoria, there is absolutely no reason at all, no evidence, that pollution has an effect on rainfall," the CSIRO's climate modelling team leader, Brian Ryan said, before adding that the climate "is so complex we can't rule anything out".

Dr Ryan said the decline in the state's rainfall was more likely the result of natural variability and the greenhouse effect.

While he agreed that the Snowy Hydro trial would be a good test of cloud-seeding technology, he said the US National Academy of Sciences this month found there was no evidence that cloud seeding worked.